Chenopodium berlandieri, also known by the common names pitseed goosefoot,[1]huauzontle, and lamb's quarters, is an annual herbaceous plant in the goosefoot family.

The species is widespread in North America, where it is native to Alaska and northern Canada south to Michoacán, Mexico, and including every U.S. state except Hawaii. The fast-growing, upright plant can reach heights of more than 3 m. It can be differentiated from most of the other members of its large genus by its honeycomb-pitted seeds, and further separated by its serrated, more or less evenly lobed lower leaves.[2]

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The species includes two subspecies: the type subspecies (i.e. C. b. ssp. berlandieri) and C. b. ssp. nuttalliae.[3] The latter, which also goes by the common names huauzontle, huauthili and Nuttall's goosefoot,[4] is a domesticated line still in cultivation in Mexico, and is distinguished by a substantial reduction in testa thickness.[3]

Additionally, the three important cultivars of the C. b. nuttalliae subspecies are:[3][5]

'Huauzontle' - This cultivar is a more recent selection used in commercial cultivation for a broccoli-like crop. It is a "naked" variety and has a testa only 2-7 µm thick (cf. human hair, which is about 100 µm wide).

'Chia' - Grown as a grain crop, this cultivar is declining and is cultivated only on a local level. It also has a very thin testa, though slightly thicker than the previous at 10-20 µm.

'Quelite' - This cultivar is also grown only locally and is likewise in decline. It is cultivated for its spinach-like leaves.

The principal difference between the wild and domesticated chenopodium is the thickness of the seed coat, the testa. In the domestic varieties because of human selection, the testa is less that 20 microns thick; the testa of wild chenopodium is 40 to 60 microns thick.[6] The species is capable of hybridizing with the related introduced European Chenopodium album, which it resembles, giving the hybrid C. × variabile Aellen.[7]

C. berlandieri is one of the plants to be domesticated in the prehistoric and Woodland periods in eastern North America, making it a part of the Eastern Agricultural Complex. Archaeological evidence shows the species was extensively foraged as a wild plant in eastern North America as early as 6,500 BC. By 1700 BC, the plant had clearly been domesticated as a pseudocereal crop. A variety of regional cultivars have been recovered from various widely separated sites. The oldest evidence for domestication comes in the form of stashes of thin-testa seeds from rock shelters in eastern Kentucky. The crop ceased to be cultivated in the region by about 1750 AD.[3]

Although cultivation of the species died out in eastern North America, the plant continues to be grown as a domesticated crop in Mexico, though its cultivation has been declining. This cultivated form of the plant is ranked as a subspecies, namely C. b. ssp. nuttalliae. Three varieties of the subspecies are grown as a pseudocereal, as a leaf vegetable, and for its broccoli-like flowering shoots, respectively.[3][5]

Based on similarities between this modern cultivated form and the archaeological specimens from eastern North America, the species was suggested to have been first domesticated in Mexico and later brought to northern North America. Currently, no archaeological evidence supports this position, with some experts even suggesting the crop may have been absent from Mexico until the 16th century. Genetic studies have shown the wild eastern North American plants and the Mexican cultivated forms have considerable genetic distance between them. This has been interpreted as indicating a later, second domestication event in Mexico.[3]